Add script library to HID attacks (and script saving functionnality)

Allow to manage a script library to quickly load pre-configured scripts in HID CMD attack and save current script for future reuse. Can be extended to Ducky ones if relevant. Tested on N7 2013 and works fully. Saved scripts are read from and written to /sdcard/files/scripts/hid (for hid scripts, another folder can be created for ducky, etc.). If the directory does not exists, it is created on-the-fly.

Requires to Update Source in order to launch a loaded script